A runaway Wisconsin teenage girl eluded Colorado police in a high speed chase, helped steal a second car and may be headed to California, police said.

Breanna Gomez, 15, has been missing from her Eau Claire, Wisc., home since Dec. 23, and is believed to be traveling with her boyfriend, Spencer Linville, 16, and two other teenage males, according to police.

The search for the group, who police believe may be heading to Riverside, Calif., is especially pressing since Gomez is insulin dependent, her grandfather, Jerry Carpenter, told ABCNews.com.

"Her insulin was left [in the car]. If she doesn't have that, she will die," Carpenter said.

Colorado police allege Gomez and three other teens outran them Thursday night during a stolen-car chase that crossed two counties.

Weld County Sheriff's Office spokesman Steve Reams told ABCNews.com that detectives believe the teens abandoned the vehicle, then took off in a stolen light blue Chrysler Town & Country minivan.

Gomez had just been released after serving six months in juvenile detention for various run-ins with police and cutting classes, her grandfather said.

"She's been troubled for a while. We've been trying to help her," Carpenter said. "She was supposed to come and see us on Sunday [and] there was even talk of placing her with us."

He implored the three teens Gomez is believed to be traveling with to "drop her off at a medical facility, a police station, anywhere."

"We love her and we just want her to get treatment," Carpenter said. "Of course she is going to have to pay the price for whatever she's doing. She's responsible for her actions, but that does not mean we love her any less."

Gomez has black hair and is described as 5-foot-6 and 150-pounds. Anyone with information is asked to contact their local law enforcement agency.